(This writeup ignores SFC III, which cleaves closely to the Star Trek: The Next Generation universe, rather than Starfleet Battles, which the earlier two are based on. Also, as I have never played the original Starfleet Command, info on that game is restricted to what I have read.)
In the Starfleet Command series of games, phasers are the
primary weapons of all races. There are nine types of phaser: Type 1, 2, 3, 4, G, G2, X, A and B. Types A and B are heavy phasers which work differently from other phaser devices, and so will be discussed separately.
All phaser-equipped ships have a phaser capacitor, which holds enough energy to completely discharge all the ship's phasers once. This allows a ship which has completely charged its phaser capacitor to be ready to fire while still using its reactor output power for other purposes, such as charging other weapons.
Type 1 phasers are the main armament of warships in the Gorn Confederation, United Federation of Planets, Romulan Empire, Mirak Star League and Interstellar Concordium. The Lyran Empire, Klingon Empire and Hydran Kingdom also use Type 1 phasers, though many of their ships use the Type 2 instead. The Type 1 draws one point of energy per shot. It is long-range and does fairly significant damage, though its destructive power fades quickly with distance. In non-X-generation games, it is the most powerful phaser that can be mounted on a starship. These phasers can be fired at missiles, fighters and other close-in threats, but will not automatically fire at them.
Type 2 phasers are the older, less advanced cousins of Type 1s. They are used by the Lyrans, Klingons and Hydrans. They also consume one unit of energy. They are shorter-ranged and slightly less damaging than Type 1, but when set to point defense, will automatically fire at missiles and fighters which come within range. Due to their large damage potential for a point-defense weapon, they are almost certain to destroy these threats in one strike. As such, they are fairly good defensive weapons, but leave something to be desired as offensive weapons. Very few designs have both Type 1 and Type 2 phasers on the same frame. The Type 2 is one of the more common phasers on heavy fighter designs.
Type 3 phasers are also known as defensive phasers. They are short-range, low-damage devices which take 0.5 units of energy to fire. Like the Type 2, they automatically engage fighters and missiles within range. While designed for point defense, the Type 3 is effective against capital ships if fired at close range. A favored tactic of many captains is to overrun their targets, then fire their after Type 3 batteries as they pass. The Type 3 is used by all races, and is the sole weapon on standard admin shuttlecraft. It also arms most of the lighter fighters and gunboats.
The Type G (for Gatling) is best described as a fully automatic Type 3. It uses one unit of energy to charge, but once charged, can fire four Type 3 blasts, using effectively 0.25 units per shot. It was pioneered by the Hydrans, but the Federation, Gorn, ISC and Mirak eventually adopted it on their late and X-generation ships as a defensive weapon. Its rapid-fire nature makes is devastating as a point defense weapon, but in close combat, it can devastate capital ships as well. Weapons of this type are the main reason why overrun tactics are suicidal when facing Hydran or late-model Federation and Mirak forces. Many late-model heavy fighters carry the Type G in lieu of the Type 2 phaser - although the Type 2 causes more damage per shot, the Type G can actually inflict more damage overall, since it fires four times.
Type G2 is an exclusively Hydran X-generation weapon. It is essentially a Type G phaser with the range of a Type 1. This makes it better against capital ships, and brutal in an escort role, often allowing a ship thus armed to plink enemy missiles as they come off the rails. Their ability to perform long-range intercepts also allows more time to react if the target is not destroyed.
Type X is another X-generation device. It is used by all empires. The Type X is effectively a souped-up Type 1 with two firing modes. In normal mode, it can fire two Type 1 blasts in one turn. In overload mode, it fires one blast with double the damage potential of a Type 1. In either mode, it uses 2 units of energy. The Type X is the standard weapon on X-generation ships, replacing the Type 1 and Type 2.
The Type 4 phaser is a starbase-mounted weapon, though two types of monsters also carry them. The Type 4 is the most powerful phaser in the game. It can inflict a significant hit at very long range, and at close ranges can cripple frigate and destroyer-class ships in one hit. | 
